Density and fertilization mode are the key factors regulating crude protein synthesis in forage maize; however, there is a lack of systematic understanding of the regulation mechanism. Here, the nitrogen/potassium ratio (N/K), free amino acid (AA) content, crude protein synthesis key enzyme activities (nitrate reductase (NR), glutamine synthetase (GS) and glutamic pyruvic transaminase (GPT)) and crude protein content and yield in leaves, stems, and grain of forage maize, as well as the relationships among them, were explored. The results showed that the N/K of DL-40 (60,000 plants per ha⁻¹, 40% N topdressing at large trumpet stage) and DH-50 (75,000 plants per ha⁻¹, 50% N topdressing at large trumpet stage) significantly increased in leaves, stems, and grain, and correspondingly, NR, GS, and GPT activities in leaves, NR activities in stems, NR and GPT activities in grain, and delayed the decline in AA content. After tasseling, for DL-40 and DH-50 the crude protein content increased by 74.1% and 39.8% in leaves, respectively, 19.9% and 25.6% in grain, respectively, and crude protein yield increased by 16.7% and 35.2% in leaves, respectively, and 23.5% and 25.9% in grain, respectively. There were significant quadratic parabolic relationships of NR, GS, and GPT activities with proportion of topdressing. There was a significant relationship of crude protein content with NR activity in leaves, with NR, GS, and GPT activities in stems and with GPT activity in grain. Regulating the key enzyme activity by adjusting the density and fertilization can significantly improve the crude protein yield of forage maize. Treatments DL-40 and DH-50 significantly increased crude protein content and yield by increasing plant N/K, NR activity in leaves, NR activity in stems, and GPT activity in grain, but slowed the decrease in AA content in leaves, stems, and grain.

Forage maize is one of the most important feed crops for livestock production, and is mainly grown in northwest China. However, their growth is often stressed by limited soil water availability due to the arid climate. To provide more soil moisture, a high-efficiency tillage technique was required to make crops effectively use soil moisture in deep soil layers. Deep vertical rotary tillage is a promising choice for this purpose. In this study, a long-term (2020–2022) field experiment consisting of three treatments, i.e., traditional tillage (TT), deep rotary tillage (DT), and deep vertical rotary tillage (VRT), was carried out in semiarid areas of Loess Plateau, northwest China, to investigate the effects of VRT on soil water storage (SWS), phase crop evapotranspiration (ET_c) during the pre- and post-flowering periods, dry matter accumulation, grain yields and the water use efficiency (WUE) of forage maize. The results showed that VRT significantly improved the absorption of soil moisture from deep layers, especially in dry years. During the pre-flowering period of a dry year (2020), VRT decreased SWS by 7.6%–10.0% in the 60–180 cm layer, and by 17.6%–18.5% in the 180–300 cm layer, respectively, compared to DT and TT. As a result, VRT increased ET_c during the pre-flowering period by 6.1% and 9.2%, respectively. In wet years (2021 and 2022), VRT increased total ET_c by 2.0%–7.9% in 2021, and by 10.1%–14.9% in 2022, respectively. On average, VRT increased the dry matter weight per plant by 1.0%–7.8%, grain yields by 2.4%–38.6%, biomass yields by 3.4%–16.2%, and WUE by 10.1%–30.0%, respectively. Particularly, the benefit of VRT for increasing yields and WUE was more noticeable in dry years. It can be concluded that VRT is a drought-tolerant and yield-boosting tillage technique that is suitable for rain-fed forage maize in semiarid areas of Loess Plateau, northwest China.

Integrated hole-sowing, fertilization, and plastic mulching techniques are common agronomic practices applied to collect rainwater and to improve rainwater utilization in semiarid rain-fed regions. However, little is known about the growth responses of tartary buckwheat (Fagopyrum tataricum L.) to the practices adopted in semiarid areas of Loess Plateau in Northwest China. To address the concerns, a long-term field experiment was conducted in 2015–2017. Four fertilization levels, namely, high fertilization level (N–P₂O₅–K₂O: 120–90–60 kg ha⁻¹, HF), moderate fertilization level (80–60–40 kg ha⁻¹, MF), low fertilization level (40–30–20 kg ha⁻¹, LF), and zero fertilization level (ZF), were applied to hole-sown tartary buckwheat with whole plastic mulching, in comparison to the control with no-mulching and zero fertilization (CK). Several key growth-influencing indicators were measured in the consecutive experimental years, including soil temperature (T_s), soil water storage (SWS), leaf area index (LAI), dry matter (DM), and grain yield. The results showed that in different precipitation years, 2015 (193 ± 23 mm), 2016 (149 ± 19 mm), and 2017 (243 ± 28 mm), the ZF, LF, MF, and HF treatments had the potential to optimize T_s in 0~25 cm soil layers (at 5 cm interval). The four treatments improved SWS in 0~300 cm soil layers by 3.5% and increased soil water consumption in the pre-anthesis period by 22.4%, compared with CK. Moreover, the four treatments shortened the pre-anthesis growth period by 0.4~5.4 d, while extended the post-anthesis growth period by 5.7~10.0 d, giving rise to an overall extension of 0.6~5.0 d for a whole growth period of tartary buckwheat. Furthermore, the ZF, LF, MF, and HF treatments increased LAI by 4.4~225.3% and DM weight by 41.5~238.0%. The rain yield of the four treatments was increased by 14.0~130.4%, and water use efficiency (WUE) was improved by 11.3~102.7%, especially for the LF treatment, compared with CK. The study indicated that the technique of hole-sowing and plastic mulching combined with a low fertilization rate was an effective measure for tartary buckwheat to optimize crop growth and to boost grain yield and WUE on semiarid lands.

Appropriate fertilization depth promotes the absorption and transport of nutrients, crop growth and yield. However, little is known about whether deep fertilization improves crude protein synthesis and how to regulate it. A two-year field experiment was conducted with various fertilization depths: (1) conventional fertilization (CF), (2) fertilization application depth at 30 cm (DF), and (3) fertilizer average application at depths of 15 cm and 30 cm (AF). The fertilization rates under all treatments were 300 kg N ha⁻¹ nitrogen fertilizer (urea, 46% N), 150 kg P₂O₅ ha⁻¹ calcium superphosphate (16% P₂O₅), and 135 kg K₂O ha⁻¹ potassium sulfate (51% K₂O). The nitrogen/potassium (N/K) ratio, the activities of nitrate reductase [NR], glutamine synthetase [GS], and glutamic pyruvic transaminase [GPT], crude protein content in leaves, stems, and grains, as well as the relationships among the parameters were explored. The result showed that deep fertilization (DF) significantly improved the N/K ratio. NR activity in DF increased by 26.30%, 35.56%, and 57.30% in leaves, stems, and grains, respectively, when compared to conventional fertilization (CF), and by 54.22%, 43.27%, and 28.44% when compared to average fertilization (AF). GS activity in DF increased by 29.67%, 47.96%, and 47.46% in leaves, stems, and grains when compared to CF, and by 40.05%, 31.51%, and 40.62% when compared to AF. GPT activity in DF was significantly higher than CF and AF in grains, and differences between treatments were significant. Crude protein content was significantly correlated with NR and GS activities in leaves, GPT activity in stems, as well as GS and GPT activities in grains. The crude protein content of leaves and grains in DF was significantly higher than in CF and AF. In conclusion, DF significantly improved crude protein synthesis and increased the crude protein content of forage maize by increasing the whole plant N/K ratio, NR and GS activities in leaves, as well as GS and GPT activities in grains. It is a highly efficient cultivation technology that significantly improves the quality of forage maize.

The Loess Plateau is a typical dryland agricultural region where water scarcity constrains crop production. Plastic film mulching is widely used to mitigate this limitation, but its long-term application has caused soil degradation and environmental pollution, highlighting the need for sustainable alternatives. This study evaluated the effects of post-wheat sequential green manure cropping—common vetch (CV) and winter rape (CR)—on soil water balance, potato yield, water use efficiency (WUE), and economic returns within a winter wheat-potato rotation system. A field experiment (2019–2023) was conducted on the Loess Plateau, comparing CV, CR, plastic film mulching (PM), and no mulching (NM). Soil water content (0–200 cm), evapotranspiration (ET), tuber yield, WUE, and economic performance were measured. Although CV and CR depleted soil water in the 0–100 cm layer during their growth, subsequent fallow precipitation (86 mm) and low soil water loss replenished the deficit, resulting in comparable soil water storage at potato sowing among CV, CR, and NM (518.8, 508.8, and 518.9 mm, respectively). Over the full rotation cycle, a positive soil water balance (63.1–147.5 mm) was maintained across all treatments, indicating no detectable net depletion within the measured 0–200 cm profile over the four potato seasons. Potato tuber yield increased by 61.7% (CV), 52.4% (CR), and 74.8% (PM) relative to NM. The WUE of CV (73.5 kg ha⁻¹ mm⁻¹) and CR (71.5 kg ha⁻¹ mm⁻¹) was comparable to that of PM (74.2 kg ha⁻¹ mm⁻¹) and significantly higher than that of NM (46.1 kg ha⁻¹ mm⁻¹). Net incomes under CV and CR did not differ significantly from PM, while their input costs were lower. Collectively, the integrated system combining post-wheat sequential green manure cropping—particularly with common vetch—and straw mulching represents a technically feasible, economically viable, and environmentally beneficial alternative to plastic film mulching, contributing to sustainable dryland agriculture on the Loess Plateau and analogous semi-arid regions.